The OpenSSL Project is a collaborative effort to develop a robust, commercial-grade, fully featured, and Open Source toolkit implementing the Transport Layer Security (TLS) protocols (including SSLv3) as well as a full-strength general purpose cryptographic library.
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RELATED CONTENT: To convert certificates from Windows to Linux click here.

The OpenSSL toolkit includes:

libssl (with platform specific naming):
Provides the client and server-side implementations for SSLv3 and TLS.

libcrypto (with platform specific naming):
Provides general cryptographic and X.509 support needed by SSL/TLS but
not logically part of it.

A command line tool that can be used for:

  • Creation of key parameters
  • Creation of X.509 certificates, CSRs and CRLs
  • Calculation of message digests
  • Encryption and decryption
  • SSL/TLS client and server tests
  • Handling of S/MIME signed or encrypted mail
  • And more…


DID YOU KNOW?: .pem, .cer, crt. are all the same type of x509/pem certificate only with different extensions.

Obtain OpenSSL:

  1. Download and install OpenSSL to perform a certificate conversion.


GOOD READING: Ivan Ristić, the creator of, has a free download of his OpenSSL Cookbook that covers the most frequently used OpenSSL features and commands. It is updated often, and is available at It is highly recommended.

Use the following OpenSSL commands to convert certificate files to different formats.

OpenSSL Commands


OpenSSL Convert PEM

Convert PEM to DER:

openssl x509 -outform der -in certificate.pem -out certificate.der

Convert PEM to P7B:

openssl crl2pkcs7 -nocrl -certfile certificate.cer -out certificate.p7b -certfile CACert.cer

Convert PEM & Private Key to PFX/P12:

openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile CACert.crt

Convert full chained PEM & Private Key (Let’s Encrypt) to PFX/P12

(a FULL certificate chain means: certificate & Intermediate/Root certificate contained in a single file)

openssl pkcs12 -export -out -inkey privkey.pem -in fullchain.pem

OpenSSL Convert DER


Convert DER to PEM:

openssl x509 -inform der -in certificate.der -out certificate.pem

OpenSSL Convert P7B


Convert P7B to PEM:

openssl pkcs7 -print_certs -in certificate.p7b -out certificate.cer

Convert P7B to PFX:

openssl pkcs7 -print_certs -in certificate.p7b -out certificate.cer
openssl pkcs12 -export -in certificate.cer -inkey privateKey.key -out certificate.pfx -certfile CACert.cer

OpenSSL Convert PFX


Convert PFX to PEM and Private Key

openssl pkcs12 -in certificate.pfx -out certificate.cer -nodes

Remove Private key password

openssl rsa -in file.key -out file2.key

Enter the passphrase and [file2.key] is now the unprotected private key.

The output file: [file2.key] should be unencrypted. To verify this open the file using a text editor (vi/nano) and view the headers.

If you need to convert a Java keystore .jks let’s say taking an SSL cert from a Tomcat system and moving it to Apache or Windows and vice-versa, it is usually easier to simply generate a new CSR key-pair from those systems and perform a re-issue of the cert, however there’s a way using a conversion application such as Portecle.

MAN Page



openssl – OpenSSL command line tool


openssl command [ command_opts ] [ command_args ]

openssl list [ standard-commands | digest-commands | cipher-commands | cipher-algorithms | digest-algorithms | public-key-algorithms]

openssl no-XXX [ arbitrary options ]


OpenSSL is a cryptography toolkit implementing the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1) network protocols and related cryptography standards required by them.

The openssl program is a command line tool for using the various cryptography functions of OpenSSL’s crypto library from the shell. It can be used for

o  Creation and management of private keys, public keys and parameters
o  Public key cryptographic operations
o  Creation of X.509 certificates, CSRs and CRLs
o  Calculation of Message Digests
o  Encryption and Decryption with Ciphers
o  SSL/TLS Client and Server Tests
o  Handling of S/MIME signed or encrypted mail
o  Time Stamp requests, generation and verification


The openssl program provides a rich variety of commands (command in the SYNOPSIS above), each of which often has a wealth of options and arguments (command_opts and command_args in the SYNOPSIS).

Many commands use an external configuration file for some or all of their arguments and have a -config option to specify that file. The environment variable OPENSSL_CONF can be used to specify the location of the file. If the environment variable is not specified, then the file is named openssl.cnf in the default certificate storage area, whose value depends on the configuration flags specified when the OpenSSL was built.

The list parameters standard-commandsdigest-commands, and cipher-commands output a list (one entry per line) of the names of all standard commands, message digest commands, or cipher commands, respectively, that are available in the present openssl utility.

The list parameters cipher-algorithms and digest-algorithms list all cipher and message digest names, one entry per line. Aliases are listed as:

from => to

The list parameter public-key-algorithms lists all supported public key algorithms.

The command no-XXX tests whether a command of the specified name is available. If no command named XXX exists, it returns 0 (success) and prints no-XXX; otherwise it returns 1 and prints XXX. In both cases, the output goes to stdout and nothing is printed to stderr. Additional command line arguments are always ignored. Since for each cipher there is a command of the same name, this provides an easy way for shell scripts to test for the availability of ciphers in the opensslprogram. (no-XXX is not able to detect pseudo-commands such as quitlist, or no-XXX itself.)

Standard Commands

Parse an ASN.1 sequence.
Certificate Authority (CA) Management.
Cipher Suite Description Determination.
CMS (Cryptographic Message Syntax) utility.
Certificate Revocation List (CRL) Management.
CRL to PKCS#7 Conversion.
Message Digest Calculation.
Diffie-Hellman Parameter Management. Obsoleted by dhparam.
Generation and Management of Diffie-Hellman Parameters. Superseded by genpkey and pkeyparam.
DSA Data Management.
DSA Parameter Generation and Management. Superseded by genpkey and pkeyparam.
EC (Elliptic curve) key processing.
EC parameter manipulation and generation.
Encoding with Ciphers.
Engine (loadable module) information and manipulation.
Error Number to Error String Conversion.
Generation of Diffie-Hellman Parameters. Obsoleted by dhparam.
Generation of DSA Private Key from Parameters. Superseded by genpkey and pkey.
Generation of Private Key or Parameters.
Generation of RSA Private Key. Superseded by genpkey.
Create or examine a Netscape certificate sequence.
Online Certificate Status Protocol utility.
Generation of hashed passwords.
PKCS#12 Data Management.
PKCS#7 Data Management.
Public and private key management.
Public key algorithm parameter management.
Public key algorithm cryptographic operation utility.
Generate pseudo-random bytes.
PKCS#10 X.509 Certificate Signing Request (CSR) Management.
RSA key management.
RSA utility for signing, verification, encryption, and decryption. Superseded by pkeyutl.
This implements a generic SSL/TLS client which can establish a transparent connection to a remote server speaking SSL/TLS. It’s intended for testing purposes only and provides only rudimentary interface functionality but internally uses mostly all functionality of the OpenSSL ssl library.
This implements a generic SSL/TLS server which accepts connections from remote clients speaking SSL/TLS. It’s intended for testing purposes only and provides only rudimentary interface functionality but internally uses mostly all functionality of the OpenSSL ssl library. It provides both an own command line oriented protocol for testing SSL functions and a simple HTTP response facility to emulate an SSL/TLS-aware webserver.
SSL Connection Timer.
SSL Session Data Management.
S/MIME mail processing.
Algorithm Speed Measurement.
SPKAC printing and generating utility.
Time Stamping Authority tool (client/server).
X.509 Certificate Verification.
OpenSSL Version Information.
X.509 Certificate Data Management.

Message Digest Commands

MD2 Digest
MD5 Digest
MDC2 Digest
RMD-160 Digest
SHA Digest
SHA-1 Digest
SHA-224 Digest
SHA-256 Digest
SHA-384 Digest
SHA-512 Digest

Encoding and Cipher Commands

Base64 Encoding
bf bf-cbc bf-cfb bf-ecb bf-ofb
Blowfish Cipher
cast cast-cbc
CAST Cipher
cast5-cbc cast5-cfb cast5-ecb cast5-ofb
CAST5 Cipher
des des-cbc des-cfb des-ecb des-ede des-ede-cbc des-ede-cfb des-ede-ofb des-ofb
DES Cipher
des3 desx des-ede3 des-ede3-cbc des-ede3-cfb des-ede3-ofb
Triple-DES Cipher
idea idea-cbc idea-cfb idea-ecb idea-ofb
IDEA Cipher
rc2 rc2-cbc rc2-cfb rc2-ecb rc2-ofb
RC2 Cipher
RC4 Cipher
rc5 rc5-cbc rc5-cfb rc5-ecb rc5-ofb
RC5 Cipher


Details of which options are available depend on the specific command. This section describes some common options with common behavior.

Common Options

Provides a terse summary of all options.

Pass Phrase Options

Several commands accept password arguments, typically using -passin and -passout for input and output passwords respectively. These allow the password to be obtained from a variety of sources. Both of these options take a single argument whose format is described below. If no password argument is given and a password is required then the user is prompted to enter one: this will typically be read from the current terminal with echoing turned off.

The actual password is password. Since the password is visible to utilities (like ‘ps’ under Unix) this form should only be used where security is not important.
Obtain the password from the environment variable var. Since the environment of other processes is visible on certain platforms (e.g. ps under certain Unix OSes) this option should be used with caution.
The first line of pathname is the password. If the same pathname argument is supplied to -passin and -passoutarguments then the first line will be used for the input password and the next line for the output password. pathnameneed not refer to a regular file: it could for example refer to a device or named pipe.
Read the password from the file descriptor number. This can be used to send the data via a pipe for example.
Read the password from standard input.




The list-XXX-algorithms pseudo-commands were added in OpenSSL 1.0.0; For notes on the availability of other commands, see their individual manual pages.


Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the “License”). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at


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